Well, only you, admins for CPF, off-site ads, and the person serving up the applet/image off of their server through links on CPF will know you IP Address...
It is not the end of the world that 3rd parties know your IP address--but it probably helps for marketing research purposes (know how many times a page has been loaded, the IP (and rough geographical location), and the router/computer that loaded the page (may be some tracking cookies in there too).
Installing NoScript will help a lot. Turning off cookies except for sites you allow, etc. See today's
FireFox thread here for a little bit more discussion and suggestions.
-Bill